<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }
    body {
        display: flex;
        width: 100vw;
        min-height: 100vh;
        background-color: pink;
    }
    main {
        /* flex: 1; */
        /* flex: auto; */
        flex-grow: 1;
    }
    footer,
    header {
        background-color: skyblue;
        height: 50px;
    }
    aside {
        width: 100px;
        height: 100vh;
        background-color: greenyellow;
        flex: none;
        overflow-y: auto;
    }
    li {
        height: 200px;
    }
    .main-container {
        flex: 1;
        display: flex;
        flex-direction: column;
    }
</style>
<body>
    <aside>
        <ul>
            <li>item</li>
            <li>item</li>
            <li>item</li>
            <li>item</li>
            <li>item</li>
            <li>item</li>
            <li>item</li>
            <li>item</li>
        </ul>
    </aside>
    <div class="main-container">
        <header>header</header>
        <main>main</main>
        <footer>footer</footer>
    </div>
</body>
</html>